Trastuzumab plus chemotherapy is an effective therapy in HER2 positive advanced gastric cancer (AGC). However, the efficacy of routine trastuzumab therapy and its association with clinicopathologic factors remain unclear. The object of the study is to determine whether the addition of trastuzumab to first-line chemotherapy improves efficacy compared with chemotherapy alone in HER2 positive AGC.

A total of 98 patients with HER2 positive AGC were enrolled in this prospective observational study. All patients were treated with trastuzumab plus chemotherapy as the first line therapy. Efficacy and safety of trastuzumab were analyzed, clinical and pathological data were collected to evaluate the potential prognostic factors on progressive free survival.

Inclusion Criteria:

1. pathology and medical imageology proven advanced gastric adenocarcinoma, inoperable;
2. received trastuzumab plus chemotherapy as the first-line palliative chemotherapy;
3. with measurable lesion with a diameter 20 mm using conventional computed tomography (CT) or magnetic resonance imaging (MRI) scans or 10 mm using spiral CT scans;
4. Eastern Cooperative Oncology Group performance status (ECOG PS ) of 0-2;
5. left ventricular ejection fraction(LVEF) more than 50 percents;
6. sufficient bone marrow, liver and renal function.

Exclusion Criteria:

1. received previous systemic therapy for advanced disease (except adjuvant/neoadjuvant chemotherapy completed at least 6 months before enrollment);
2. trastuzumab based adjuvant/neoadjuvant therapy;
3. treatment with any other anticancer therapy (lapatinib, immunotherapy, etc);
4. patients with heart failure, coronary artery disease or myocardial infarction within the previous 6 months.
5. trastuzumab based first line therapy started beyond 4 weeks from the first diagnoses of AGC.

Patients diagnosed with HER2 positive advanced or metastatic gastric adenocarcinoma in Shanghai Zhongshan Hospital, Fu Dan University were prospectively collected. HER2 expression was assessed by IHC first. In the cases with IHC 2+, fluorescence in situ hybridization (FISH) was used to detect HER2/neu amplification levels.